Pyrotechnic grenades of a variety of types are known, including flash grenades and smoke grenades. Smoke grenades generate a volume of smoke after initiation, and are principally used for signalling, and concealment of movement. They are used in a variety of contexts, including military, maritime (as distress flares) and recreational (for example, in battle simulation or “paintball” or “airsoft” games).
Typical design consists of a container with emission holes to allow smoke release when the grenade is ignited. The filler consists of smoke composition (typically potassium chlorate, lactose, and a dye). The reaction is exothermic, and considerable heat is generated during smoke release.
To use the grenade, the smoke mixture must be ignited, and this is generally achieved by means of a fuse. Types of fuses known in the art include friction strike fuses, in which a primer button is provided with a cap whose outside surface is partially coated with a friction-ignitable material. This friction-ignitable material is in turn covered with a removable cover provided with a striking plate or section covered with red phosphorus or an abrasive material. To ignite this type of device the user must first remove the cover from the friction-ignitable material. The end of the cover with the scratch material is then rubbed or struck quickly across the friction-ignitable material to ignite the flare mixture.
A further type of ignition mechanism is generally referred to as a pull-wire. One type consists of an elongated tube, having an inner wall coated with friction-ignitable material. A pull-wire runs through the channel and the free end projects out of one end of the tube, while at the other end the wire is attached to a plunger coated with scratch material. To operate the fuse, the user pulls the free end of the wire, causing the plunger to travel down the tube, causing frictional force between the plunger and the friction-ignitable material, and combustion of the latter. This, in turn, ignites a primer charge and ultimately the smoke mixture.
A further type of pull-wire igniter includes a wire which passes through a hole in a metal cup, with one end of the wire coiled or bent adjacent to the open side of the cup, and the other protruding out of the cup and attached to a ring-pull. The cup contains an ignition mixture. On pulling the ring-pull, the wire is pulled through the hole in the ignition mixture and cup straightening it and generating heat through friction, which ignites the ignition mixture.
A problem with both the strike ignition and pull-wire type fuses is that the device is in the hand of the operator when ignition commences. This is a burn hazard for the user, and additionally it may be undesirable in certain circumstances for smoke generation to commence at the location of the operator, who may for tactical reasons desire to throw the device so as not to disclose their location.
One solution to this problem is shown in FIG. 1.
The fuse mechanism in the grenade (10) includes a safety pin (11) inserted through a hole (12). The safety pin (11) in the hole (12) holds a safety lever (13) against the side of the grenade body (14). The safety lever (13) in position against the body (14) of the grenade (10) holds a spring loaded lever (15) against the top of the canister containing the smoke material (16). The spring loaded lever (15) is attached to one end of a pull-wire (20), the other end of which forms a coil (17) inside metal cup (18). Metal cup (18) contains a pyrotechnic composition, typically a chlorate/fuel mixture.
Removal of the safety pin (11) permits release of the safety lever (13), which then has to be held against the body (14) of the grenade (10) to prevent ignition. Once the grenade (10) is thrown, the pressure on the safety lever (13) is released, and the spring loaded lever (15) is forced to rotate on its axis by the spring (19), throwing off the safety lever (13). The spring loaded lever (15) then exerts an upward force on the pull-wire (20), forcing the coiled portion (17) through an aperture in the metal cup, which generates heat and in turn ignites the friction-ignitable material and ultimately the smoke material (16).
Although this type of fuse overcomes certain limitations inherent in pull-wire type fuses, it nevertheless has drawbacks. In particular, the force exerted on the pull-wire can be hampered by the safety lever, leading to unreliable ignition. Further, the spring exerts a significant upforce on the safety lever, which can result in a significant “kick” when the primed grenade is thrown, leading to inaccuracies in deployment and potential ignition failures.
In addition, as soon as the safety lever (13) starts to move away from the body of the grenade (14), the spring loaded lever (15) also starts to rotate. If the safety lever (13) is released slowly, the spring loaded lever (15) also rotates slowly pulling the pull-wire (20) with insufficient speed or force to generate sufficient friction to ignite the friction-ignitable material within the metal cup (18). This causes a significant unreliability in the ignition of the smoke material (16).
The present invention seeks to overcome these and other limitations of prior art devices.